The injection of additional air directly after the combustion chamber results in the afterburning of the hot exhaust gas. On one hand, this “exothermic reaction” reduces the amount of the exhaust-gas components, hydrocarbons (HC) and carbon monoxide (CO), and, on the other hand, heats the catalytic converter.
By this means, the conversion rate in the warm-up phase of the catalytic converter is considerably increased, which is particularly necessary for vehicles having very low emissions.
In conventional methods, the secondary air is switched in in an abrupt manner.
In addition, secondary-air injection systems of the applicant are known, in which controllable secondary-air pumps are used whose air mass flow rates are separately measured. The mass of air is then preferably notched up, using a ramp whose slope is appliable, but constant. In conventional secondary-air injection systems and methods for controlling the amount of secondary air, it is problematic that the amount of secondary air is not adaptable to the heating progression in the catalytic converter. This results in a conversion rate, which is not optimal and can lead, in extreme cases, to pollutants such as hydrocarbons (HC) ending up in the exhaust gas (so-called hydrocarbon (HC) breakthroughs).